Without acoustic treatments you could just about place them anywhere. Treatments are easy to construct and would be a wise move for an area that big. I made my own for my home theater, and in the process of making more for a buddy of mine. I would just experiment on placement of them after you get your sauna put in and anything else that you would consider "fixed" in place.
I may end up having to do this. I was hoping to get a general idea because I'm running RCA's through a conduit to the house to my main receiver, and the leads to my speakers are only 25 ft or so, so not a huge amount of room to play.
I guess it doesn't really matter. If I setup the room lengthwise, I'll be getting first reflections of the side walls pretty bad. If I set it up wide, I'll be getting first reflections off the back wall (opposite the speakers) pretty bad.
Not sure I'm going to go as far as acoustical treatments in here!
It's just a high powered garage setup, and I'm wanting to avoid reflections, nodes, standing waves, etc. as much as possible.
Maybe in the centre of the room, on opposite ends of the garage, facing in, mounted up near the ceiling would be decent???
AH CRAP, I'LL JUST HAVE TO F* AROUND WITH IT WHEN I GET THERE!
To be honest, I'm 3500km from home working for a while, and I'm so exited about getting my first house that I can't sit still, so I'm trying to plan out everything to do with the stereo stuff.
Before I move anything in I'm going to go and pre-wire everything in my living room, so I can put in the proper boxes, and then mud around them, and repaint the whole room. It's too light in the living room right now so I'm going with some sort of red wine colour or something.